The investigators have identified areas of the brain that are activated in response to disease-related emotional information, following whole lung allergen challenge in asthma. They propose that activity in these central nervous system locations, as measured by fMRI, is associated with the intensity of allergic inflammation, provoked by segmental bronchial challenge, in the absence of significant airflow obstruction. The investigators predict that this relationship will be mediated by changes in expression of genes in the IL-1β/IL-17 pathway.